Hi Rugxulo, Anton, some more ideas through the list again :-)

> MS-DOS works well with MS-HIMEM loaded by PXE the same way.
> FreeDOS just hangs while trying to load MS-HIMEM.

Rugxulo, is that something that has happened before?
I am not sure but this sounds vaguely familiar. The
driver (from Win98-DOS?) might depend on some property
of the Win98 / DOS boot loader and/or kernel here...



> FreeDOS loads HIMEMX fine with DOS=LOW, but any DOS/32A application has
> failed with memory corruption error (6004).

At least it loads - that gives the possibility to try some
of the HIMEMX command line options to see if any of those
fixes the memory corruption...

As mentioned, you have a number of configuration choices:

/VERBOSE (to see which A20 method is used etc)
/TESTMEM:ON (obvious, but might be a dummy option)
/LOG (to show all activity on the screen, noisy)

/METHOD:PORT92 or BIOS or ALWAYSON or BIOS or or KBC or FAST or PS2
(PORT92, FAT and PS2 are the same with different sanity checks...)

/NOABOVE16 (to ignore int 15.e801 reports about high memory)
/X (to ignore int 15.e820 reports about high memory)
/MAX=number (to use at most number kB of high memory)



> FreeDOS + JEMMEX (NOEMS) loads fine, DOS32/A app (curl) works fine, but 
> "bupdater" from Asus has failed as I've posted screenshort early.

For JEMMEX, the options are A20METHOD:PORT92 (or KBC, PS2, FAST,
BIOS or ALWAYSON) and NOE801 and NOE820 to ignore the respective
int 15 reports about high memory. The latter can be useful if a
more low-level driver such as the PXE boot loader or MEMDISK (if
you use that?) provides inconsistent reports for different int15
"BIOS" memory map interfaces.

Note that if you use JEMMEX, it will only switch the real A20
at special moments, mostly during start. From the application
side, it will simulate the A20 by changing 386+ memory maps.

However, JEMMEX probably does not protect you from switching
A20 directly with all methods (keyboard controller, port 92,
BIOS) instead of using the HIMEM-style interface for this.

So if your software, for example bupdater, uses interfaces
not covered by the JEMMEX A20 simulation, your software can
switch the real A20, bypassing JEMMEX and getting a conflict.
There also is a JEMMEX option NOA20 to disable the emulation.

Other interesting options are ALTBOOT, NOCHECK, NOHI, NOVME,
PGE, VERBOSE, EMX, X=TEST, NORAM, NOINVLPG etc. - Admittedly
too many options, but include some possibly useful sanity
checks, workarounds and block-risky-feature items. See the
docs or send the output of JEMMEX /? to a file or view it
page-wise using the MORESYS console device driver :-) Some
of the options can also be switched on the fly, reducing
the number of reboots required for testing those...



> I can try to load FreeDOS from USB stick instead of PXE.

That might also be interesting, yes.

Regards, Eric



PS: Maybe somebody can tell us which A20 methods actually
are trapped by JEMMEX for the simulated/emulated A20 side
and for which methods there is a risk of bypassing JEMMEX.
That risk might be different for protected mode apps, too.



------------------------------------------------------------------------------
CenturyLink Cloud: The Leader in Enterprise Cloud Services.
Learn Why More Businesses Are Choosing CenturyLink Cloud For
Critical Workloads, Development Environments & Everything In Between.
Get a Quote or Start a Free Trial Today. 
http://pubads.g.doubleclick.net/gampad/clk?id=119420431&iu=/4140/ostg.clktrk
_______________________________________________
Freedos-user mailing list
Freedos-user@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/freedos-user

Reply via email to